Photo-electric cell



T. W. CASE.

PHOTO-ELECTRIC CELL.

APPLICATION man AUG-27, 1920.

1,376,605. Patented May 3, 1921;

Source vf Altzruai'in Cur-ran? Q ,Gi/i ZZVTOR ATTO zur s UNITED STATES PATENT OFFICE.

'rnnononn w. oAsn, orscirro, NEW xoax.

PIBOTO-ELECTRIC CELL.

" Specification of Letters Patent.

Patented MayS, 1921.

Application filed August 27, 1920. Serial No. 406,463.

State of New York, have invented new and.

useful Improvements in Photo-Electric Cells, of which the following, taken in connection with the accompanying drawings, is a full, clear, and exact description.

This invention relates to certain improvements in photo-electric cells.

The object of the invention is to produce a highly efficient cell of the character described, and which shall be of simple construction, unusually constant and uniform in reaction, and relatively permanent in its activity. v

Other objects and advantages relate to the details of construction of the cell, all of which will more fully appear from the following description, taken in connection with the accompanying drawings, in which Figure 1 is a diagrammatic view illustrating a methodof carrying out onestep'of the process of producing the cell.

, Fig. 2 is a diagrammatic view illustrating a manner of use of the cell of this invention.

The completed cell of this invention consists of a vacuum tube inclosing a plurality of electrodes, one of which is provided with a coating of barium deposited thereon in a manner to be hereinafter described.

The invention, however, contemplates and permits of the introduction of a quantity of v an inert gas, such-as argon or helium, into the vacuum tube containing the electrode.

Under such circumstances, it may be suggested #that the photo-electrons emitted by the action of light ionize the inert gas by ime pact resulting in maximum conductivity. i

It is believed at present that the constant and uniform re-action of the cell, its relative permanency of activity and great-intensity are largely the result of the peculiar structural form of one of the electrodes of -the cell due to the peculiar and novel method of.

manufacture.

The physical structure of the coating of metal deposited upon one of the electrodes is not at present known with absolute certainty, and the theory of the action that results in the unexpected sensitivity of the element so produced is more or less a matter for intelligent speculation, and the applicant hesitates .to state positively any definite theory, and desires to confine himself to the demonstrated fact that the element so produced is highly sensitive and relatively permanent in its activity, but with this reservation, it may be suggested as indicative of applicants present theory, that the metal deposited in the form of a coating upon one or the electrodes is in a peculiar structural condition resultant from the fact of its deposit in the manner to be described under constant bombardment by cathode rays or electrons.

The process of manufacture described and This coating may be produced upon the filament in any suitable way, as by dipping the same in-barium nitrate at a suitable temper-- ature to cause the same to flow upon the filament, and, by incfease in temperature, change the nitrate to an oxid.

The coated filament is then placed in an ordinary glass tube or bulb opposite a me tallic electrode, as, for instance, a nickel plate. The bulb is then evacuatedand the whole isbaked at such a temperature as may be suitable for eliminating practically all traces of gases. Then the filament and metallic electrode are preferably connected in a circuit with a source of sufliciently high potential so as to heat the metallic electrode red hot, thus driving off from the metalllc electrode any remaining traces of gases and I oxygen.

The electrode temperature is then reduced by regulating the potential to that found by experiment most suitable under the circumstances for the particular operating conditions without heating the electrode to a red heat. A suitable circuit is provided contain-. ing a source of potential for heating the filament to such a temperature as will result in throwing off the said filamentcoating in the form of relatively small particles.

By connecting the filament and metallic electrode in a circuit containing a suitable I source of potential, the thrown-ofi? material of the coating applied to the filament is, to a very large" extent, caused to be deposited upon the metallic electrode. In other words, the high potential existing between the electrodes acts as a directive agency and causes the thrown-ofi' material to deposit upon the plate in a thin layer, where it is continuously bombarded by the cathode rays, or lectrons, emanating from the filament and directed by the potential of the metallic electrode.

'It is found that when a filament, as described, is coated with barium oxid, that the 'oxid is lost when th material is finally derays of the material deposited on the plate.

' During-this. step of the operation, the tube or bulb is connectedto a suitablevacuum pump for maintaining a substantially complete vacuum within the bulb.

[This condition may be maintained for stated intervals, as, for instance, five minute periods, and after each such period the photo-electric qualities of the cell may be tested in comparison with a constant source oflight, and when the maximum re-action is obtained, the vacuum pump may be shut ofi, and the tube containing the filament and metallic electrode sealed.

During the process of manufacture when using a direct current the potential in the circuit is so arranged as to maintain a positive potential upon the metallic electrode and a negative potential upon the filament.

In Fig. 1 I have diagrammatically illustrated a hook-up suitable for carrylng out the depositing step of this process in which the filament -1 is connected in an independent heating circuit '2 with a source of potential 3 and in which the. circuit between the filament -1 and metallic elec-- trode 2- includes the secondary -4 of a transformer, the primary 8- of which is connected in circuit'with a suitable source of alternating current. The secondary of the transformer embodies a "considerably larger number of coils than the rimary to When e process roducing the co is com leted, as de as an unheated electrode, and any other form of electrode may be substituted. In .Fig. 2 I have illustrated the cell in a hook-up suitable for measuring light intensity in which two electrodes are connected in circuit with a source of potential -7- and "a galvanome'ter 5-. Variations in the light rays to which the cell (which includes the electrodes -l and 2 and the vacuum tube or bulb 6) is exposed, will be accuratelyjndicated in a known standard of measurement by the galvanometer -5. The process above described permits of practically. perfect control in the manufacture of cells of uniform action. Further, the method ofi'ers a substantially perfect control in obtaining the desired spectral sen sitivity of the cell by combining the proper substances on the filament to be deposited on a between the electrodes and proper temperatrue.

What I claim is 1. A photo-electric cell including an electrode having a coating of barium.

2. A photo-electric cell including an electrode comprising barium.

3. A photo-electric cell including an electrode having a thin coating comprising barium.

4. A photo-electric cell including an electrode having a coating of barium deposited under bombardment by cathode rays.

5. A photo-electric cell including an. electrode comprising barium deposited under bombardment by cathode rays.

6. A photo-electric cell including an lectrode having a thin coating comprising barium deposited under bombardment by with ode rays.

7.-A photo-electric cell comprising a plurality o mentary form. 5

8. A photo-electric cell comprising a filaing light sensitive material thrown off from the filament and deposited on the other electrode under bombardment, by cathode rays.

In witnem whereof I have hereunto set mentary electrode and an electrode comprlselectrodes, one of which is of fila- 

